Key cards of varied form are widely used to insert in receivers which identify the cards to permit holders of cards to enter a premises, to enter data or to receive data or materials.
Many cards have electronic circuit elements embedded in the card or have magnetic information retained in the card or have some other form of identification.
Cards with magnetic storage of identification are susceptible to inadvertent change in the stored magnetic information, and data and cards having embedded circuit elements are relatively expensive and are difficult to produce and change and use.
The present invention overcomes problems which are inherent in the prior art.